Safety and health concerns are now arising about the quality of drinking water, in particular, tap water, and removal of harmful substances (e.g., free residual chlorine, trihalomethanes, and mold odors) contained in drinking water is being desired. Heretofore, for the removal of these harmful substances, water purifiers having a housing filled with a granular activated carbon have been mainly used. In particular, trihalomethanes dissolved in tap water in minor quantities are suspected to be a carcinogen. With a recent increase in health consciousness, a water purifier by which trihalomethanes can be removed takes on a growing importance.
The present applicant reported a water purifier provided with, as a cartridge, a molded activated carbon for removal of trihalomethanes in Japanese Patent No. 4064309 (JP-4064309B, Patent Document 1; the molded activated carbon is produced by mixing 100 parts by weight of a fibrous activated carbon having a specific surface area of 1000 to 1800 m2/g, 10 to 300 parts by weight of a powdery coconut-shell or phenol resin-series activated carbon having a median particle size of 10 to 70 μm and a capacity to adsorb benzene of 25 to 40% by weight, and 3 to 30 parts by weight of a fibrous binder to give a mixture, dispersing the mixture in water to give a slurry, and integrally molding the slurry by a slurry suction method.
In a case where the cartridge formed from the molded product is set in a container, such as a housing (a casing), it is necessary to further compress the cartridge on a workbench in order to improve the shape of the cartridge. Unfortunately, the compression treatment (rolling treatment) results in the cartridge decreasing in a capability to filter out turbidity components (impurities) probably due to the compression of the surface of the cartridge.
Moreover, the present applicant reported, in WO2011/016548 (Patent Document 2), a molded activated carbon as a filter being capable of increasing the removal of turbidity components in addition to harmful substances (such as trihalomethanes); the molded activated carbon is formed from a mixture containing a powdery activated carbon having a median particle size of 80 to 120 μm and a specified standard deviation in a particle size distribution and a fibrous binder. The molded product is highly capable of removing free residual chlorine, volatile organic compounds, CAT (2-chloro-4,6-bisethylamino-1,3,5-triazine), and 2-MIB (2-methylisoborneol) as measured according to Japanese Industrial Standards (JIS) S3201(2004) and has an improved filterability of turbidity components compared with a conventional activated carbon. Further, this document discloses that the compression to arrange (or form) the shape of the molded product should be minimal since excessive compression may result in consolidation of the surface of the molded product.
Unfortunately, in a case where the molded product is set in a housing, a lot of molded products are discarded due to a low dimensional accuracy thereof, so that the yield is low. The improvement of the yield requires the compression to arrange the shape of the molded product, although the compressed product has a low capability to remove the turbidity components.